Asphalt composition



Patented Sept. 15, 1942 UNITED STATES PATE NT OFF ASPHALT COMPOSITION Stanley S. Sorem, Berkeley, Calif., assignor to Shell Development Company, San Francisco, Calif., a corporatiop of Delaware a No Drawing. ,Application June 29, 1940,

Serial No. 343,270

. 15 Claims. (Cl. 117-135) asphalt forms avery poor bond with the gal-' vanized metal. In many instances, particularly when water is present, the asphalt will be completely removed from the galvanized surface within a few weeks time.

It is therefore the object of this invention to provide an asphaltic composition which will maintain a firm bond with galvanized surfaces indefinitely even in the presence of water. It is a further object to provide a method for the neutralization of asphalts.

It has been found that the reason for the disbonding of normal asphalts from the galvanized surfaces lies in the presence of free acids such as naphthenic and/or asphaltogenic acids in the asphalt. Almost all asphalts including both natural asphalts such as Trinidad asphalt and manufactured asphalt, i. e. those produced by the distillation of petroleum oils, contain some asphalt which soaps are no more soluble in water than the corresponding zinc soaps. able metals include aluminum, lead, zinc, iron, tin, antimony, bismuth, arsenic, copper and mercury. Because of their greater activity, the first three are preferred.

As a result of the incorporation of the salts into the asphalt, soaps are formed causing at least partial neutralization of the acids originally present, and releasing at least a portion of the acid of the added salt. However, the released acid is often as detrimental in that it may not only be as harmful in the matter of disbonding as the. asphaltic acids which were neutralized but also prevents the neutralization from going to completion.

It has been found when heating the asphalt cyanic and the like. Inasmuch as the halogen acid. Blown asphalts produced by air blowing 1 asphalts at elevated temperatures (or by equivalent chemical treatment such as with chlorine or sulfur) contain particularly large amounts of acid. Asphalts ordinarily have'acid numbers ranging from about .1 to about 5 (mg. of KOH per gm. of asphalt-A. S. T. M. test D188-27T) These acids react with the zinc of the galvanized surface to form zinc salts, thereby destroying the bond which links the asphalt and the galvanized surface and causing the asphalt to become separated from the surface. It has been attempted to neutralize these acids with caustic alkalis such as potassium, sodium and calcium hydroxides,. but this neutralization has been found to be ineffective since the salts so formed attack the zinc almost as rapidly, possibly because oLdifierences in solubilities of the second salts involved. Therefore, the net result is about the same as though the free acid were present.

It has now been found that salts combining certain metals with volatile acids may. be added to asphalts for the purpose of neutralizing the .acids found in asphalts. The metals which are suitable for the purpose of this invention are those forming soaps (or, more properly, salts) with the asphaltogenic or naphthemc acids of acid salts may act as catalysts promoting condensation, polymerization, oxidation and-the like when heating the asphalt, salts .of non-halogen acids are usually preferred when it is desired to retain the original physical properties of the asphalt.

The heating of the asphalt and salt may be done in suitable refinery equipment such as in a blowing still .or distillation unit. Preferably a gas such as air, steam or chlorine is blown through the heated asphalt to aid in the removal of acids. The removal of the volatile acid may be effected in conjunction with steps in the manufacture of asphalt such as blowing or distilling.

If a straight run asphalt is being prepared, the

salt is preferably added to the topped crude oil prior to or during the distillation in which the asphalt is obtained. This can conveniently be done by injecting the salt into the flash tower. In the distillation of crude oils which due to their corrosive nature are ordinarily treated by the addition of an alkali such as lime, the salts of the present invention may be used to supplant, in whole or in part, the lime or other alkali. When the salt is added during areflnery operation as described above, the heating will ordinarily be sufilcient to drive substantially all of the free, liberated, volatile acid from the asphalt except when a halogen acid. salt is used. ,In the latter instance, the acid is frequently not fully removed during the blowing or distilling in which Suitcase steam should be blown through the asphalt to complete the removal. When the salts are added to natural or previously prepared asphalts, the mixture must be heated to a temperature of from 200 to 600 F. for about two hours preferably accompanied by blowing to insure substantially complete removal of the free acids.

The amount of the salt which is used will depend upon the acidity of the asphalt to be treated, or, if the treatment is combined with a blowing operation, on the acidity that the asphalt would develop on blowing were no salt present. The initial content of the salt should be at least one and preferably two equivalent weights per equivalent weight of acid present or potentially present in the asphalt. To secure satisfactory results, the acid number of the asphalt should be reduced to a maximum of 1.5. Some asphalts are known to have appreciable acid numbers but lower than 1.5; these are bcnefitted as well by the treatment with the salts of the invention, since even traces of acid render asphalts objectionably corrosive for many applications.

To illustrate the present invention, the following examples are given of its application:

Sheets of galvanized iron were coated with a film of asphalt 005mm thick. The sheets were immersed in Water and the time noted when the asphalt firststarted to peel. The asphalt used had an acid number of 4.3 and samples of it were mixed with two equivalent weights of various salts per equivalent weight of acid present. Some of the samples were heated to a temperature of 450 to 500 for 2 hours to facilitate reaction and to drive off the free acids, while others were blown with air at a temperature of 450 to 500 F.

The following results were obtained:

Method Time Material added to asphalt of of treatment peeling None 3 (lays. Aluminum chloride 10 days. Lead acetatc 6 weeks. Do 8 weeks. Zinc acetate 8 weeks.

The method of neutralizing the acids of asphalt by converting them to soaps possesses the further advantage of imparting a greater tendency of the asphalts to adhere to wet stones, it being well known that water-insoluble soaps increase the adhesiveness of asphalt toward wet stones.

I claim as my invention: 1. The process of improving the bonding power of an asphalt containing normal amounts of asphaltic acids towards a metallic surface corrodible by said acids comprising adding to said asphalt a small amount of a salt combining a volatile organic acid with a metal the soaps of which metal with said asphaltic acids are no more water-soluble than those of zinc, heating the asphalt to expel volatile acids and applying the resulting product to said metallic surface.

5. The process of claim 1 in which the heating is carried out at a temperature of about 200 to 600 F. for about two hours.

6. The process of claim 1 in which the heating is carried out at a temperature of about 450 to 500 F.

7. The process of claim 1 in which the amount of salt added to the asphalt is about one equivalent weight of the acid in said asphalt.

8. The process of claim 1 in which the amount of salt added to the asphalt is about two equivalent weights of the acid in said asphalt.

9. The method of improving the bonding power toward zinc of an asphalt containing asphaltic acids and having an acid number of above 1.5 comprising adding to said asphalt an amount of a salt combining a volatile organic acid with a metal, the soaps of which metal with said asphaltic acid are no more water soluble than those of zinc, said amount being at least equivalent to said acid number, heating said asphalt under conditions to expel volatile acids until the acid number has been reduced to below 1.5 and applying it to a zinc surface.

10. The method comprising adding to a topped crude oil containing a normal amount of petroleum acids during the process of manufacturing asphalt therefrom a small amount of a salt of a volatile organic acid and a metal, the soaps of said metal with asphaltic acid being less soluble in water than the corresponding zinc soaps under conditions to free and expel part at least of said organic acid and coating a metal surface corrodible by said asphaltic acids with the resulting asphalt.

11. The method of claim 10 in which the topped crude oil is distilled in the presence of the said salts.

12. The method of claim 10 in which the asphalt is blown in the presence of the said salts.

13. The process comprising at least partially neutralizing asphaltic acids by adding to an asphalt containing normal amounts of said acids a salt combining a volatile organic acid with a metal chosen from the group consisting of aluminum, lead, zinc, iron, tin, antimony, bismuth, arsenic, copper and mercury, heating the resulting mixture to volatilize free acid; and applying the resulting product to a metallic surface cor rodible by said asphaltic acids.

14. The process of producing permanent bonds between a metal corrodible by asphaltic acids and asphalt comprising normal amounts of such acids which comprises treating said asphalt With a salt combining a volatile organic acid with a metal the soap of which with said asphaltic acids is no more water-soluble than a zinc soap, under conditions to free and expel a portion at least of said volatile acid, and thereafter applying said asphalt to said corrodible metal.

15. The process comprising treating an asphalt containing normal amounts of asphaltic acids with a salt combining volatile organic acids and a metal whose soaps are no more water-soluble than those of zinc, under conditions to expel part at least of said volatile acids, and applying the resulting product to a metallic surface corrodible by said asphaltic acids.

STANLEY S. SOREM. 

